The present invention pertains to the suppression of undesirable fugitive emissions or fume that is prevalent in the pouring of molten metal, particularly that of iron or steel.
When molten metals are poured from one container to another in various metal production processes the pouring is accompanied by the emission from the receiving container of large amounts of fume. One typical example is the transfer of refined steel into a receiving ladle upon tapping of the converter or steelmaking furnace.
The generation of such fugitive emissions constitutes a serious atmospheric pollution problem associated with many metallurgical processes, the abatement of which represents a significant part of the cost of performing these processes. Much effort and expense has been expended in the development of emission control systems that are effective to maintain the volume of fugitive emissions within acceptable limits. These efforts are exemplified by the arrangement of various forms of air or gas curtains and fume exhaust equipment to isolate the affected region of the plant and to conduct the undesirable effluent to treating apparatus prior to its discharge into the atmosphere. Such systems are exemplified by U.S. Pat. Nos. 3,396,954, granted Aug. 13, 1968 to Krogsrud; 3,834,293, granted Sept. 10, 1974 to Danieli; and 3,994,210, granted Nov. 24, 1975 to Davis. These systems all rely on the capture and disposal of the fugitive fume and, while being effective to a limited degree in solving the concerned problem, entail significant capital expenditure to install and are costly to operate.
In Japanese Pat. No. 53-6602, granted Mar. 9, 1978 to Nippon Steel Corporation, on the other hand, is described an emission control system by means of which fugitive fume is controlled by spraying an inert gas, typically steam or nitrogen, into the molten metal receiver. Spraying is achieved by an ejector ring that is suspended into the vessel to position it closely above the level of the molten bath. The ring is suspended by a hoist that enables the ring to be raised as the bath level rises thereby to maintain a relatively constant spacing between the ejector ring and the bath surface.
Although this gas ejector of the Japanese patent is an improvement over prior art devices of the aforementioned type in that it is effective to suppress to a limited extent the formation of fume, its use is not totally dispositive of the problem. Firstly, the ejection of steam or nitrogen onto a molten bath has been found to be not, by itself, capable of suppressing the generation of fume to an acceptable level. Tests conducted by applicants indicate that fume suppression in this manner is only about seventy percent effective. Secondly, the need to maintain the ejector ring closely adjacent the level of the bath subjects the equipment to the possibility of damage due to the extremely high temperature environment in which it is used and to the danger of contacting the bath itself or being impinged upon by splashing metal which plugs the gas ejection ports thereby to rapidly render the ring inoperative.
It is to the solution of the above problem and to the development of a more effective manner of suppressing the emission of fugitive fume from molten metal operations that the present invention is directed.